The primary purpose of this Phase I/II trial is to establish the safety of administration of the I-131 labeled MN-14 IgG (Anti-Carcinoembryonic Antigen Monoclonal Antibody) and to determine the maximum tolerated does (MTD) and does limiting toxicity (DLT). The DLT is almost always related to bone marrow toxicity, and to this end frequent monitoring of blood counts is performed in the period following administration of the therapeutic dose. In addition, the study will also evaluate by CT and FDG-PET the response of tumor to therapeutic doses of the antibodies. The possible development of antibody response to the administered antibodies will be monitored as well. The data obtained from these preliminary phases will be used to further design trials to evaluate the safety and efficacy of the radiolabeled antibodies.